Hi Uma,
Below is a reply I've posted in the past on this topic. Ken.
Hi,
As others have said this is a tricky issue. The odds of you getting a
succesful postback are 50/50 to say the best. I've had about a 95% success
rate doing this:
1. Capture the onbeforeunload event in your body tag.
2. Incorporate the WebService.htc.
3. When the onbeforeunload event fires run a function that uses the
WebService.htc to tell a web service.
The browser will close before you get a response back but, about 95% of the
time, your web service will get hit and the user can successfully be logged
out. Note, that using the latest IE and Windows XP you will achieve almost
100% results. This is sort of complicated until you get the hang of it. If
this isn't something you want to try then here is another suggestion to
improve your chances but it might seem clunky to the user:
Have a main page that the user browses to. To run your app, they click a
button or link and then you use window.open() to create a new browser
window. This is the window your app runs from. Don't ask me why, but the
success rate of a postback from onbeforeunload seems to be much higher for
browsers launched from javascript than from browsers launched by the user.
Good luck! Ken.